Significantly enhanced oxygen vacancies in W18O49 nanowires for electrochromic films by annealing in argon

Abstract

Owing to the energy-efficient attributes of electrochromic technology, there has been a growing emphasis on the fabrication of electrochromic devices with high-contrast and stable performance. As an electron donor, the deliberate incorporation of oxygen vacancies into an electrochromic material is poised to significantly elevate the film's electrochromic characteristics. In this study, we successfully synthesized one-dimensional W18O49 nanowires thin films with enhanced oxygen vacancies using a straightforward combination of solvothermal reactions and annealing in Ar. In comparison to films annealed in air, those treated in argon (Ar) exhibited a higher concentration of oxygen vacancies, resulting in improved light absorption characteristics. The optimal annealing conditions were determined to be 400 °C for 40 min. Under these conditions, the thin film demonstrates enhanced electrochromic performance, exhibiting a notable 71.6% modulation in transmittance, a 27.2% increase compared to the air condition. It displays a rapid response time (Tb = 3.3 s, Tc = 3 s), high coloration efficiency (CE = 55.9 cm2 C−1), and excellent cycling stability (with a ΔT retention rate of 93.9% after 750 cycles).